void MergeList ( LinkList &L1, LinkList &L2 ){
    LNode *p1 = L1->next, *p2 = L2->next;
    L1->next = NULL;
    while(p1 && p2){
        if(p1->data <= p2->data){
            LNode *q = p1;
            p1 = p1->next;
            q->next = L1->next;
            L1->next = q;
        }else {
            LNode *q = p2;
            p2 = p2->next;
            q->next = L1->next;
            L1->next = q;
        }
    }
    if(p2) p1 = p2;
    while(p1){
        LNode *q = p1;
        p1 = p1->next;
        q->next = L1->next;
        L1->next = q;
    }
}